Metric threading


carbure2003
 


lance
 

Nice projects.
Quite ambitious by my thinking.

_L_
+++

On Feb 25, 2018, at 3:58 PM, 'guycad@...' guycad@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:

I just completed a small winter project

I made a transposing gear set for metric threading on SB 9A or 10K.



Next gear project will be to cut a 80T idler gear out of delrin for the SB gear train. I want to see how it will reduce gear train noise. It seems that most of the noise comes from the meshing of the 20T gear with the idler gear. Last year I manufactured a delrin gear for the reverse thumbler and noise significantly reduced.

Guy Cadrin


carbure2003
 

WHEN indexing gear teeth the important is to count...... I screwesd on one gear because I made a full turn instead of 1 3/4 turns.

Good practice is to rotate the gear blank with the indexing set- up in order to be confortable with the routine.

When your dividing head has more than one solution for indexing a specific number of teeth, take the largest circle.... it is easier because you have more strength while rotating. If I had to change something on my dividing head, I would put two handles on the dividing arm.

It was a fun project. Not cost efficient if you plan on selling them. I have seen nice CNC setups on ebay.

Guy Cadrin

---------- Original Message ----------
From: "Lance Eggleston gbof@verizon.net [SOUTHBENDLATHE]" <SOUTHBENDLATHE@yahoogroups.com>
To: SOUTHBENDLATHE@yahoogroups.com
Subject: Re: [SOUTHBENDLATHE] Metric threading
Date: Sun, 25 Feb 2018 20:19:28 -0500



Nice projects.
Quite ambitious by my thinking. _L_+++On Feb 25, 2018, at 3:58 PM, 'guycad@netzero.com' guycad@netzero.net [SOUTHBENDLATHE] <SOUTHBENDLATHE@yahoogroups.com> wrote:I just completed a small winter projectI made a transposing gear set for metric threading on SB 9A or 10K.Next gear project will be to cut a 80T idler gear out of delrin for the SB gear train. I want to see how it will reduce gear train noise. It seems that most of the noise comes from the meshing of the 20T gear with the idler gear. Last year I manufactured a delrin gear for the reverse thumbler and noise significantly reduced.Guy Cadrin

____________________________________________________________
Wendy Williams Confirms Unfortunate News
risingstarnewspaper.com
http://thirdpartyoffers.netzero.net/TGL3241/5a938745c974374520d3st01vuc


roefa.excite
 

RE: "It was a fun project. Not cost efficient if you plan on selling them. I have seen nice CNC setups on ebay."
 
...not to mention the solid and hollow 3D printed ones on Youtube by MrPete222 aka Tubalcain.
Cheers !
Roger Memphis
 

-----Original Message-----
From: "'guycad@...' guycad@... [SOUTHBENDLATHE]" [SOUTHBENDLATHE@...]
Date: 02/25/2018 10:05 PM
To: SOUTHBENDLATHE@...
Subject: Re: [SOUTHBENDLATHE] Metric threading


WHEN indexing gear teeth the important is to count...... I screwesd on one gear because I made a full turn instead of 1 3/4 turns.

Good practice is to rotate the gear blank with the indexing set- up in order to be confortable with the routine.

When your dividing head has more than one solution for indexing a specific number of teeth, take the largest circle.... it is easier because you have more strength while rotating. If I had to change something on my dividing head, I would put two handles on the dividing arm.

It was a fun project. Not cost efficient if you plan on selling them. I have seen nice CNC setups on ebay.

Guy Cadrin


---------- Original Message ----------
From: "Lance Eggleston gbof@... [SOUTHBENDLATHE]" <SOUTHBENDLATHE@...>;
To: SOUTHBENDLATHE@...
Subject: Re: [SOUTHBENDLATHE] Metric threading
Date: Sun, 25 Feb 2018 20:19:28 -0500



Nice projects.
Quite ambitious by my thinking. _L_+++On Feb 25, 2018, at 3:58 PM, 'guycad@...' guycad@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...>; wrote:I just completed a small winter projectI made a transposing gear set for metric threading on SB 9A or 10K.Next gear project will be to cut a 80T idler gear out of delrin for the SB gear train. I want to see how it will reduce gear train noise. It seems that most of the noise comes from the meshing of the 20T gear with the idler gear. Last year I manufactured a delrin gear for the reverse thumbler and noise significantly reduced.Guy Cadrin

____________________________________________________________
Wendy Williams Confirms Unfortunate News
risingstarnewspaper.com
http://thirdpartyoffers.netzero.net/TGL3241/5a938745c974374520d3st01vuc


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Kelly Howerton
 

 
I have a set of metric gears for my 9 but have yet to get counter to sync with them just have to set each cut into the thread. Any simple answers? Thanks


m. allan noah
 

The imperial thread dial is useless with metric threads. You either need to leave the halfnut engaged, or use the technique half-way down this page: http://conradhoffman.com/metricthreading.htm

allan

On Mon, Feb 26, 2018 at 1:09 PM, Kelly Howerton kellyhowerton@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:
 

 
I have a set of metric gears for my 9 but have yet to get counter to sync with them just have to set each cut into the thread. Any simple answers? Thanks




--
"well, I stand up next to a mountain- and I chop it down with the edge of my hand"


DJ Delorie
 

"Kelly Howerton kellyhowerton@yahoo.com" writes:
I have a set of metric gears for my 9 but have yet to get counter to
sync with them just have to set each cut into the thread. Any simple
answers? Thanks
I had a similar problem with my model 34 and ended up 3d-printing that
part: http://www.delorie.com/photos/southbend-lathe/img_3133.html

(of course, I 3d-printed the metric gears too :)


DJ Delorie
 

"'m. allan noah' kitno455@gmail.com" writes:
The imperial thread dial is useless with metric threads. You either
need to leave the halfnut engaged, or use the technique half-way down
this page: http://conradhoffman.com/metricthreading.htm
Well, not *totally* useless, as you need to have it to use that
technique (which I use). You just have to use it differently.

Also, that technique in video form:
https://www.youtube.com/watch?v=HXt4TWa382Q

You could also combine it with inverse threading so you don't have to
disengage in a panic: https://www.youtube.com/watch?v=Z-dqOi_z5bk


sblatheman
 

Another alternative is to use an IN/METRIC thread dial (METRADIAL)
I have one of those for sale. Fits the 9”, 10K, or Heavy 10 

Ted

On Feb 26, 2018, at 1:28 PM, DJ Delorie dj@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:

 


"'m. allan noah' kitno455@..." writes:
> The imperial thread dial is useless with metric threads. You either
> need to leave the halfnut engaged, or use the technique half-way down
> this page: http://conradhoffman.com/metricthreading.htm

Well, not *totally* useless, as you need to have it to use that
technique (which I use). You just have to use it differently.

Also, that technique in video form:
https://www.youtube.com/watch?v=HXt4TWa382Q

You could also combine it with inverse threading so you don't have to
disengage in a panic: https://www.youtube.com/watch?v=Z-dqOi_z5bk


eddie.draper@btinternet.com
 

Round numbers.  That is what this is about.  Cutting imperial ptiches using an imperial pitch leadscrew, the ratios of the numbers of revolutions required of workpiece and leadscrew is always a nice round number, not too high.  The same goes for cutting metric threads using a metric leadscrew.  Try to cut metric with an imperial screw or v v and the ratios required shift you away from nice round numbers and so the leadscrew gets out of phase with the threads on the job.  A reversing lathe is virtually essential, as the lathe HAS to be reversed, whether the split nut is temporarily disengaged and then re-engaged IN THE SAME PITCH or not.  Run it forward enough revolutions and the job and leadscrew will eventually come back in phase, but you have no way of detecting easily when that happens.

Incidentally, I assume that most folk reading this will be more familiar with imperial screwcutting.  It's a bit simpler than metric screwcutting, as you only need one pinion for the screwcutting dial to engage with the lead screw.  Our Colchester Triumph 2000 (all metric, but also with a wide range of imperial pitches, see above for the requirements for using these) has 4 alternative pinions with different numbers of teeth for the screwcutting dial, each matching a certain group of metric pitches.  I assume other metric lathes with a decent range of pitches are the same.

I have a question for those who use changewheels:  25.4 x 5 = 127.0, 5 being the first multiplier that results in a whole number of teeth, so does a wisely deployed 127 tooth gear provide EXACT metric pitches?  The ratio between inch & mm was defined as exactly 25.4 in the 1930s.  The metric unit is the base standard.  I suppose the inches on earlier lathes might be a bit different, as the American National survey inch differed by about 1/8" per mile.

Eddie



From: "DJ Delorie dj@... [SOUTHBENDLATHE]"
To: SOUTHBENDLATHE@...
Sent: Monday, 26 February 2018, 18:33
Subject: Re: [SOUTHBENDLATHE] Metric threading

 

"'m. allan noah' kitno455@..." writes:
> The imperial thread dial is useless with metric threads. You either
> need to leave the halfnut engaged, or use the technique half-way down
> this page: http://conradhoffman.com/metricthreading.htm

Well, not *totally* useless, as you need to have it to use that
technique (which I use). You just have to use it differently.

Also, that technique in video form:
https://www.youtube.com/watch?v=HXt4TWa382Q

You could also combine it with inverse threading so you don't have to
disengage in a panic: https://www.youtube.com/watch?v=Z-dqOi_z5bk



DJ Delorie
 

"Edward Draper eddie.draper@btinternet.com" writes:

I have a question for those who use changewheels: 25.4 x 5 127.0, 5
being the first multiplier that results in a whole number of teeth, so
does a wisely deployed 127 tooth gear provide EXACT metric pitches?
Yes. A 127-to-something conversion essentially converts your leadscrew
from "some imperial pitch" to "some metric pitch" (because 127mm is
exactly 5in, so whole numbers :). You still have the complexity of
*what* pitch, of course :-)

(note: it doesn't convert the physical TPI of the leadscrew, hence the
threading dial issues mentioned before)


jonwoellhaf
 

Which begs the question, “Why did they decide to define the millimeter to be exactly 1/25.4 of an inch? Why not 1/25th?”
 

From: DJ Delorie dj@... [SOUTHBENDLATHE]
Sent: Monday, February 26, 2018 15:06
To: SOUTHBENDLATHE@...
Subject: Re: [SOUTHBENDLATHE] Metric threading
 
 


"Edward Draper eddie.draper@..." writes:

> I have a question for those who use changewheels: 25.4 x 5 127.0, 5
> being the first multiplier that results in a whole number of teeth, so
> does a wisely deployed 127 tooth gear provide EXACT metric pitches?

Yes. A 127-to-something conversion essentially converts your leadscrew
from "some imperial pitch" to "some metric pitch" (because 127mm is
exactly 5in, so whole numbers :). You still have the complexity of
*what* pitch, of course :-)

(note: it doesn't convert the physical TPI of the leadscrew, hence the
threading dial issues mentioned before)


DJ Delorie
 

"'Jon Woellhaf' jonwoellhaf@comcast.net" writes:
Which begs the question, “Why did they decide to define the millimeter
to be exactly 1/25.4 of an inch? Why not 1/25th?”
Well, the inch was defined by some ancient king's finger, and the meter
by some random planet's circumference... so go blame them :-)

And BTW, the inch is currently defined as 25.4mm, not the other way
around. Go figure.

Also BTW the meter is now defined in terms of the speed of light.
Slightly less random, but just as arbitrary :-)


jonwoellhaf
 

As long as we’re being pedantic, “... speed of light in a vacuum.”
 

From: DJ Delorie dj@... [SOUTHBENDLATHE]
Sent: Monday, February 26, 2018 15:49
To: SOUTHBENDLATHE@...
Subject: Re: [SOUTHBENDLATHE] Metric threading
 
 


"'Jon Woellhaf' jonwoellhaf@..." writes:
> Which begs the question, “Why did they decide to define the millimeter
> to be exactly 1/25.4 of an inch? Why not 1/25th?”

Well, the inch was defined by some ancient king's finger, and the meter
by some random planet's circumference... so go blame them :-)

And BTW, the inch is currently defined as 25.4mm, not the other way
around. Go figure.

Also BTW the meter is now defined in terms of the speed of light.
Slightly less random, but just as arbitrary :-)


ww_big_al
 

The (international) inch has been exactly 25.4 mm since July 1959. At this point in time the (international) yard was redefined as 0.9144 metre - until this time the ratio between the US yard and the metre was different to the ratio between the UK yard and the metre. For more information, see Engineering Metrologyby K J Hume (2 ed) Macdonald London 1967. The American inch changed by 2 millionths of an inch and the UK inch by 1.7 millionths of an inch. The international inch falls mid way between the old UK and US inch.

References:

  • The Yard Unit of Length, Nature, Vol 200, No 4908 pp 730-732 23 Nov 1963
  • The United Kingdom standards of the yard in terms, of the metre (British Applied Journal of Physics)
In other word, history. 


Rick Rick
 

I use a Sherline electronic rotary table for cutting gears. One push of the button and you are at the next cut.
So very simple, but somewhat expensive solution.
Rick


fwhite913
 

Trying to reach Latheman...

Fred


sblatheman
 

Send an email:

On Feb 27, 2018, at 3:00 PM, 913fred@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:

 

Trying to reach Latheman...

Fred


Paul Alciatore
 

Why 25.4mm instead of 25.0? Well, both the inch and the meter were already established when today's standard was adopted in the 1950s and the 1960s. Both had gone through several refinements before that point and more problematic was the fact that different countries had slightly different standards, at least for the inch. When the 25.4mm factor was adopted as the exact conversion, that distance for the inch was 1.7 millionths longer than the existing imperial inch and 2 millionths shorter than the existing US inch. I believe other countries also had differences. In short, it was a compromise and, being only a three digit number, it was a very convenient one. Two parts in a million was almost a negligible difference for almost all practical purposes.

If the inch had been redefined as 25mm at that time, then that would have been a difference of almost 1.7% and that would have been noticeable on almost every ruler and other measuring device that used inches. Virtually every one of them in the world would have been instantly inaccurate and would need to be replaced. Just for one example, a one foot ruler would be off by about 3/16". Even a first grade school child would notice. The confusion in the world of engineering would be enormous.

But, as I said above, the 25.4mm figure was only off by millionths of an inch. So, a 100 foot tape measure would only be off by 0.0002". For all practical purposes every existing measuring device could be used with no worry about it's accuracy. Only the most demanding measurements in physics and astronomy would need to ever consider the differences between the old standards and the new one.

So the 25.4mm figure was a magnificently practical compromise. I was getting my degree in physics (the science of measurement) in the early 60s and there was absolutely no reason to correct for the change in any of the experiments or calculations that I did in that program. The blueprints for bridges and buildings and automobiles and everything else were just as good after the change as before. And the same measurement devices were still used with no problems.


john kahrs
 

Awesome. What a concise and detailed rundown. Not only the how- but the *why* a great 20th-century definition of standards finally settled into its final form.